Patients that have been identified as having a chronic physical condition, such as a cardiac disorder, are managed in a variety of ways. For some, devices such as a pacemaker or a cardiac defibrillator may be implanted into their body. Implantable medical devices (“IMDs”) may be designed to perform a variety of functions. These functions include stimulation of body organs, drug delivery, and simple monitoring of physiological conditions of a patient. Most IMDs operate independently of any external inputs; but occasionally the devices need to be recharged, reprogrammed, or otherwise checked to ensure proper performance. Typically, a communication interface is provided between the IMD and an external monitor to reprogram and monitor the IMD. Unfortunately, such communication interfaces are very short-range due to the limited size and power allowances of the IMD. Additionally, in most cases today, recharging of the IMD device is an invasive procedure which creates trauma for the patient. To accomplish recharging, the IMD is removed, recharged, and replaced in a surgical procedure after a predetermined time or when the battery charge level is deemed “low.”
Due to the short-range communication limitation, activities such as monitoring, maintenance, and programming of an IMD must be performed using equipment in close proximity to the IMD. Typically, such monitoring and maintenance requires an IMD patient to visit a physician's office where the physician can communicate with the IMD by opening a low frequency communication channel. Once the channel is open, the physician can reprogram the IMD, conduct a performance check, and perform any other diagnostic functions deemed necessary. Although this form of IMD interface communication has worked well, there is a need to bring IMD patients into a more efficient and less restrictive communication paradigm. It is cumbersome, time-consuming, and costly for patients to visit a physician's office to have an IMD reprogrammed. It is also cumbersome and costly to conduct and/or schedule transtelephonic pacer checks, which require application of a magnetic field at the patient's skin over the area where the IMD is located.
Furthermore, in the event an implanted cardiac defibrillator discharges, it is extremely important that a record of the event is captured and a physician is notified almost immediately. Prior solutions to the need of physician notification include devices that would notify a physician when the patient manually triggered the notification process. However, if a patient had a heart-attack, stroke, or other debilitating event, the patient may not be able to trigger the communication device, and a doctor would not be notified. Thus, it is desired to provide a means of remote and continuous monitoring of a patient's IMD performance without requiring patient-initiated surveillance of the IMD.
Longer range communication systems have been proposed to be implemented within the IMDs themselves. In U.S. Pat. No. 6,083,248, Thompson discloses a system in which a transceiver is incorporated within the IMD. This system provides a long-range communication system that enables remote monitoring of the IMD. The transceiver communicates with an external patient communication control device that is worn by the patient, or otherwise located in close proximity. The external control device is linked with a remote medical support network. This system is further described in U.S. Pat. No. 5,752,976 to Duffin & Thompson.
One problem with the use of a transceiver within an IMD, as described in the above-referenced patents, is that it does not address the needs of patients having older IMDs that do not incorporate such a transceiver. Another problem with the transceiver being located within the MD itself is the increased size of the IMD, making the IMD unsuitable in some applications. Additionally, a high powered transceiver may interfere with the operation of the IMD if located within the IMD. Thus, the IMD becomes a more complicated device, leading to an increased failure rate, which is unacceptable in life-threatening situations.
Another problem encountered when the transceiver is incorporated within the IMD is there is no way to verify that the IMD is operating properly. Specifically, there is no verifiable way to ascertain whether or not the IMD is accurately sensing the patient's actual condition as intended by the physician who programmed the IMD. There is also no verifiable way to determine whether the IMD is responding to the physiological conditions to which it was designed to respond. Put another way, there is no verifiable way to ascertain whether the IMD is performing like it “thinks” it is.
In U.S. Pat. No. 5,626,630 Markowitz describes a transceiver that can be adapted for use with new and old IMD's; however this transceiver must be electrically connected to the IMD. This fact makes this solution unworkable for patients with preexisting implants because it would require the removal and rewiring of the IMD. In addition, if a patient who currently has an IMD wired to an implanted transceiver, as described by Markowitz, needs to have a second IMD implanted, the surgical procedure is further complicated by the need to physically wire the already-implanted transceiver to the new IMD.
Further to the disclosure of the patents discussed above, remote two-way communication is also possible with implantable devices by utilizing the system described in Kail U.S. Pat. No. 5,959,529. The Kail Patent enables communication from an ambulatory subject to a monitoring center. However, the system described by Kail does not provide for communication with, monitoring, and programming an MD within a patient.
Thus there is a need to enable communication with IMDs that will not require a visit to a physician's office and will not necessarily require any pre-scheduling. There is also a need to provide a means for more constant monitoring of an IMD while allowing the patient to be mobile and free. Specifically, there is a need to monitor, periodically or continuously, the performance of an IMD within a patient to determine whether the IMD is operating as intended without inhibiting the patient's mobility or freedom. In the event the IMD is not operating properly, or a patient is in an emergency condition, there is a need for automatic physician notification. It is also desired to provide a transceiver that can monitor and otherwise communicate with multiple IMDs in a patient without being electrically connected to the IMD. In addition, there is a need to provide a transceiver that is capable of communicating with old, pre-existing IMDs as well as newly implanted IMDs.